Category Archives: Kitchen Science

Does the Aussie “pie and sauce” protect against sunburn?

The classic Australian meat pie advertisement shows tough men in shorts eating a pie with tomato sauce (similar to ketchup) in the blazing sun.

But could this quintessential Down Under delicacy help to protect Aussie skins from the harmful effects of UV radiation?

Sunlight can cause the formation of free radicals in the skin cells. Free radicals are atoms which exist with an unstable number of electrons in an electron shell. Ultraviolet (UV) radiation can “force” electrons from atoms such as oxygen and create free radicals. Since the electron state of a free radical is so unstable, they are likely to react with anything they touch in the cell – be it a protein or DNA strand. This can lead to temporary damage (such as sunburn) or permanent damage including cataracts – and even to cancers such as melanomas.

Tomatoes contain caretenoids such as lycopene. These are the chemicals which give tomatoes their rich colour. Lycopene is perhaps the most powerful of the anti-oxidants found in any fruit or vegetable.

Anti-oxidants react with oxygen (and other) free radicals to neutralise them before they can harm biological processes. To some extent, the more anti-oxidant molecules in a cell, the more likely a free radical is to hit one of those before hitting a vital part.

Putting caretenoids – especially lycopene – onto the skin has been shown to help prevent and even partially reverse the damage done by exposure to UV light. But it’s not just an external form of sun block – leaving the sauce your pie provides benefits too.

A diet rich in tomatoes has been shown to reduce sunburn and the effects of UV exposure. In fact concentrated cooked tomato (such as tomato paste or sauce) is an even better source of such anti-oxidants than are fresh tomatoes. Forty grams (4 tablespoons) of tomato paste eaten daily has been shown to significantly reduce visible sunburn after only a few weeks.

While not a substitute for sunblock or sun-safe practices, eating a diet rich in tomatoes could thus provide some level of continuous protection. Indeed, it is likely that increasing tomato consumption in your diet may help protect not only against sunburn, but the visible signs of aging, cataracts and skin cancer.

Perhaps in the “sunburnt country” of Australia, it is no coincidence that tomato sauce became the condiment of choice.


Aust O, Stahl W, Sies H, Tronnier H, Heinrich U (2005) Supplementation with tomato-based products increases lycopene, phytofluene, and phytoene levels in human serum and protects against UV-light-induced erythema.
Int. J. Vitam. Nutr. Res. 75(1):54-60.

Fazekas Z, Gao D, Saladi RN, Lu Y, Lebwohl M, Wei H (2003) Protective effects of lycopene against ultraviolet B-induced photodamage Nutr. Cancer 47(2):181-7.

Stahl W, Heinrich U, Aust O, Tronnier H, Sies H (2006) Lycopene-rich products and dietary photoprotection. Photochem Photobiol Sci. 5(2):238-42.

Stahl W, Heinrich U, Wiseman S, Eichler O, Sies H, Tronnier H (2001) Dietary tomato paste protects against ultraviolet light-induced erythema in humans. J. Nutr. 131(5):1449-51.



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Better salad dressings II – natural emulsifiers and creamy milk

To make more stable salad dressings (see previous post), you need a chemical which can help to suspend the oil particles in the water-based liquid. Mustard and cayenne pepper are natural emulsifiers which can help to suspend oil in water. Adding these to a vinaigrette will slow the mix from separating after you shake it.

Egg yolks (these contain lecithin) are used to emulsify mayonnaise. It’s easy to test how good an emulsifier these are by shaking them with a little water and oil and seeing how long the mixture takes to settle back into layers.

Milk is a mix of fats and liquids. If you leave fresh milk to sit for a while, the fat will eventually settle out, leaving a cream layer. This can be collected for sale as cream, or used to make butter. To prevent this, milk for drinking is homogenised. This involves forcing the milk at high pressure through a narrow opening. Cream globules are broken into very small droplets. These have larger surface areas, and are more spread out throughout the milk. This and the emulsifiers naturally found in milk (including casein and lecithin) allow the cream to stay evenly distributed throughout the liquid for longer.Thus the milk you buy in the supermarket does not have a cream layer even when left to stand for a few days.

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Tipsy on bubbly

Champagne has no more alcohol than many wines, yet most drinkers notice that you feel tipsy faster.

It’s not just a feeling. One study suggests that the blood alcohol levels rise more quickly after drinking champagne (or any sparkling wine) compared to a still wine. This increased impairment lasts for 20 minutes, until still wine drinkers “catch up” with the inebriation levels.

Why would this be?

Flattened champagne acts like a regular wine, so it must be something to do with the bubbles.

Bubbles in sparkling wines are carbon dioxide. In expensive wines, these are a product of active yeast. In cheaper wines, this is artificially added, in the same way as soft drinks are carbonated.

So how does carbon dioxide bubbles help to move alcohol into the bloodstream?

Very little alcohol passes through the stomach walls, most is absorbed from the small intestine. It is possible that bubbles push against the sphincter muscle closing the stomach, encouraging it to open and permit faster gastric emptying. Since alcohol would then hit the small intestine earlier, it could be absorbed more quickly.

It really needs more research. I’m sure there would be no shortage of volunteers for studies looking at relative rates of inebriation.

But this raises some extra questions. Does fizzy beer make you drunk faster than still? What about sparkling cocktails versus still ones? Do carbonated soft drinks raise blood glucose levels more quickly than flat cordials?

Plenty of research ideas for the budding scientist (alcoholic?).


Ridout F, Gould S, Nunes C, Hindmarch I. (2003) The effects of carbon dioxide in champagne on psychometric performance and blood-alcohol concentration. Alcohol Alcohol. 38(4):381-5.

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Chocolate sweetens pregnancy

A couple of decades ago, a number of babies were born with classic heroin withdrawal symptoms – restlessness, inability to sleep, sweating and irritability. Their mothers strongly resisted the suggestion that they were junkies. After further investigation, it was discovered that all mothers were heavy coffee drinkers. Caffeine withdrawal in babies appeared equivalent to withdrawal from strong illicit drugs.

In fact, research seems only to find more ways in which caffeine and reproduction do not mix. One cup of brewed coffee a day halves a woman’s chances of conceiving (probably due to spontaneous abortion). The effect on babies may be more far-reaching. Crossing easily over the placenta, caffeine can build up in foetal tissue. Just 2 or 3 (brewed) cups a day during pregnancy reduces infant birthweight and retards development. In fact rodent studies suggest that effects may reach beyond the first generation, with grandchildren also potentially affected by heavy caffeine use.

Stopping caffeine once pregnant may not prevent all problems. Caffeine consumption in the menstrual cycle prior to conception may affect the health of future children. Similarly heavy caffeine consumption can damage sperm quality.

Most prenatal health guides now recommend low caffeine intake for expectant mothers. Caffeine is present in varying amounts in numerous foods and beverages including coffee, tea and soft drinks (such as colas).

With so much bad news about caffeine and reproduction, chocaholics must become quite depressed when facing pregnancy. However recent reports suggest that the news may not be as bleak as first thought. Contrary to popular belief, chocolate has very limited quantities of caffeine. Instead it contains another compound, theobromine. Like caffeine, theobromine is a stimulant with mood altering properties. Theobromine is also found in lower quantities in tea, but not in coffee. While dark chocolate has shown possible, limited health benefits, milk and white chocolate do not appear to have any such benefits – probably due to the high fat and high sugar content.

In terms of pregnancy, two studies have shown the benefits of moderate consumption of chocolate during pregnancy.

A recent study by Maconochie et al, from the London School of Hygiene and Tropical Medicine has linked regular chocolate consumption with reduced first trimester (<13 weeks) risk of miscarriage. They showed a slight but significant drop in miscarriage rates for women who consumed almost daily chocolate.

Another study from Finland showed mothers who consumed daily chocolate whilst pregnant rated their children as more happy (increased laughter/smiles, reduced crying) at 6 months of age. Interestingly, whilst maternal stress during gestation was a predictor of fear in 6 month old babies, this was largely negated by chocolate consumption. This could mean that maternal chocolate consumption could not only improve the temperament of babies, it could reduce the known effects of maternal stress (whilst pregnant) on new-borns*.

But be warned. Excess chocolate consumption during pregnancy also appears to lead to withdrawal symptoms in infants. Moderation is the key!

* (Note: the study did not adjust for continued maternal chocolate intake after birth – chocolate in breastmilk could account for differences in baby temperament. The authors also suggest that chocolate could improve maternal mood and thus mother/child interractions and results in children could be a result of psychological benefits rather than/as well as physiological benefits. I also wonder if continued chocolate consumption merely made mothers perceive their children as happier. It certainly makes me see the world as a happier place.)


Cambria S, Manganaro R, Mami C, Marseglia L, Gemelli M. (Pre-print online 2006) Hyperexcitability Syndrome in a Newborn Infant of Chocoholic Mother. Am J Perinatol.Eskenazi, B. (1999). Caffeine: Filtering the Facts. New England Journal of Medicine, 341(22), 1688-1689.

Maconochie N, Doyle P, Prior S, Simmons R. (Pre-print online 2006) Risk factors for first trimester miscarriage – results from a UK-population-based case-control study. BJOG: An International Journal of Obstetrics & Gynaecology

McGowan JD, Altman RE, Kanto WP Jr. (1998) Neonatal withdrawal symptoms after chronic maternal ingestion of caffeine. South Med J. 81(9):1092-4.

Pollard, I (1994) A Guide to Reproduction: Social Issues And Human Concerns Cambridge University Press.

Raikkonen K, Pesonen AK, Jarvenpaa AL,Strandberg TE. (2004) Sweet babies: chocolate consumption during pregnancy and infant temperament at six months. Early Hum Dev. 76(2):139-45.


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Recipe for beer bread

Now you can harness the goodness of beer
at breakfast time (and not on your cornflakes) .
This is a quick and easy recipe using the yeast in beer to make the bread rise. It is only partially leavened however, so it’s only good straight out of the oven. Beer was historically made from bread and now can be used to make great bread.


1 bottle (stubbie or can) of beer
3 – 3.5 cups of plain bread flour

In a bowl, mix 3 cups of flour and the beer with a large spoon. Keep adding flour until the dough stops sticking to the sides of the bowl and forms a nice elastic lump in the centre. Put this lump in a loaf tin (or similar). Bake at about 200 degrees Centigrade (395 degrees Fahrenheit) for about 45 minutes or until the loaf sounds hollow when you knock on it. The bread should fall out of the pan.
It’s nice spread with butter.

My husband is Russian and so we also eat beer bread by peeling cloves of fresh garlic, dipping these in salt and rubbing the outside crust of the bread. This makes a sort of garlic bread and ensures that you can enjoy the benefits of both beer and garlic at breakfast-time.

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Let’s hear it for beer!

Beer has been consumed for at least five or six thousand years. Prayers, recipes and descriptions have shown it was integral to the inebriation of people from ancient civilizations including the Sumerians, Egyptians, Babylonians, Romans and Greeks.

Some historians go so far as to suggest that the craving for beer created civilization itself. Hunter gatherer societies began farm crops and to build towns in response to the need to stay in one place long enough to permit fermentation and brewing. Fortifications and armies were formed to protect the essential grain crops.

Whether beer provided the impetus for civilization or not, it was certainly a crucial (if not the primary) source of nutrients in early societies.

Naturally beer has changed substantially over the centuries. Originally formed by fermenting bread, it would have barely had a fizz let alone the frothy head we know today. Hops were a later addition and thus early beers differed remarkably from the bitter flavor of current western beer.

While for most people, beer is no longer a major source of nutrition, beer today still contains a wide range of essential compounds including proteins, antioxidants and B vitamins. With such a powerhouse of ingredients, it has the potential to be good for you. But is it?

As usual, the answer lies in the quantities in which it is consumed. While 10 beers may seem like a great idea on a Friday night, generally Saturday’s hangover reminds us that moderation is the sensible course. In large quantities, beer, like any other alcoholic beverage can cause nausea, headaches and in the long term, liver disease, brain deterioration and cancers including mouth, oesophagus, liver, lung and colon.

But in moderation, then how good for us is beer?

First let’s define moderation. Moderation is equivalent to (or less than) 1 standard drink a day for women and two for men.

Beer is high in B vitamins – vitamins important in mood regulation, promoting healthy tissue growth, boosting the immune system and preventing anemia.

Like red wines, beer protects the cardiovascular system, with moderate beer drinkers having only a third the risk of coronary heart disease than a non (or heavy) drinker. The magic ingredients in both wine and beer appear to be the anti-oxidants, polyphenols (found in hops and malt) – and beer contains as much polyphenol as wine. These are chemicals which prevent the oxidation of low-density lipoproteins (LDLs) – also known as “bad” cholesterol. “Bad” and “Good” cholesterol are misleading terms. Cholesterol is good for you to some extent – it allows you to be solid at room temperature. However transporting cholesterol in LDLs damages the arteries through oxidation. Cholesterol carried as high density lipoproteins is considered “Good cholesterol” as it does not cause atherosclerosis to the same extent. A beer a day increases the amount of HDLs by 4.4%.

Studies following people for at least 10 years have shown that moderate alcohol intake (including beer) has also been shown to reduce the risk of type 2 diabetes by 36% for men and 58% for women. It seems like isohumulones, responsible in part for the bitter flavors in beer, reduce the insulin levels in the blood. They also help to prevent (and can be used to reduce) hypertension.

Beer can act as an antiviral – inhibiting the replication and thus spread of numerous viruses including HIV.

Beer is also high in phytoestrogens – plant similies of the hormone estrogen. These phytoestrogens are what supposedly makes soy products beneficial. While beer has yet to be fully tested, it is possible that constituents may help to regulate circulating hormone levels thus improving mood, reducing cholesterol and possibly preventing some cancers.

Beer can even protect against radiation damage (from things like x-rays) with numerous studies showing better survival rates after high dosage radiation in animals given beer extracts, and protection of lymphocytes in human blood. Some of this is due to cancer prevention compounds. Beer constituents have been shown to reduce free-radical levels in the blood and to prevent some DNA damage associated with early tumours. In animals, this has been demonstrated as a reduced risk of colon cancer.

For the more elderly, beer seems especially beneficial. It has been shown to counter osteoporosis (weakening of bones associated with broken hips and other bones) with regular drinkers showing reduced bone mass loss.

It also slows dementia onset. For people 55 and older, moderate alcohol (including beer) drinkers showed better cognitive function than their teetotal (or inebriated) peers. Don’t take your gran out to lunch – take her to the pub!

On the downside, beer does give you the munchies. However studies have shown that beer consumption does not lead to a higher body mass index (BMI) and can reduce weight gain under some circumstances – in other words the beer gut is an urban myth. Obviously, like any alcohol it’s not beneficial during pregnancy as it can cause physical and behavioural problems in the child. The only other negative thing I found about beer was that regular consumption increased the amount of bleeding after operations.

Overall, beer does appear to be a bit of a wonder drug – so long as you lay off the stubbies a couple of weeks before the hospital visit and if you are expecting.

So perhaps it really is as Benjamin Franklin once said that “beer is proof that God loves us and wants us to be happy.”


Braidwood R.J., Sauer J.D., Helbaek H., Mangelsdorf P.C., Cutler H.C., Coon C.S., Linton R., Steward J., Oppenheim A. L. (1953) Symposium: Did Man Once Live by Beer Alone? American Anthropologist, 55( 4): 515-526

Denke MA. (2000) Nutritional and health benefits of beer. Am J Med Sci. 320(5):320-6.

Eckardt MJ, File SE, Gessa GL, Grant KA, Guerri C, Hoffman PL, Kalant H, Koob GF, Li TK, Tabakoff B.(1998) Effects of moderate alcohol consumption on the central nervous system. Alcohol Clin Exp Res. 22(5):998-1040

Gerhäuser, C. (2005) Beer constituents as potential cancer chemopreventive agents. European Journal of Cancer, 41(13) : 1941-1954

Jugdaohsingh R, O’Connell MA, Sripanyakorn S, Powell JJ. (2006) Moderate alcohol consumption and increased bone mineral density: potential ethanol and non-ethanol mechanisms. Proc Nutr Soc. 65(3):291-310

Kondo K. (2004) Beer and health: preventive effects of beer components on lifestyle-related diseases. Biofactors. 2004;22(1-4):303-10.

Monobe M, Uzawa A, Hino M, Ando K, (2005) Glycine betaine, a beer component, protects radiation-induced injury. J Radiat Res 46(1):117-21

Monobe M, Koike S, Uzawa A, Ando K. (2003) Effects of beer administration in mice on acute toxicities induced by X rays and carbon ions. J Radiat Res 44(1):75-80.

Monobe M, Arimoto-Kobayashi S, Ando K. (2003) Beta-pseudouridine, a beer component, reduces radiation-induced chromosome aberrations in human lymphocytes. Mutat Res. 538(1-2):93-9.

Monobe M, Koike S, Uzawa A, Aoki M, Takai N, Fukawa T, Furusawa Y, Ando K.(2004) Radioprotective activities of beer administration for radiation-induced acute toxicity in mice. Radiother Oncol. 73 Suppl 2:S127-9.

Monobe M, Ando K. (2002) Drinking beer reduces radiation-induced chromosome aberrations in human lymphocytes. J Radiat Res 43(3):237-45.

Negrao MR, Keating E, Faria A, Azevedo I, Martins MJ. (2006) Acute effect of tea, wine, beer, and polyphenols on ecto-alkaline phosphatase activity in human vascular smooth muscle cells. J Agric Food Chem. 54(14):4982-8.

Stampfer MJ, Kang JH, Chen J, Cherry R, Grodstein F. (2005) Effects of moderate alcohol consumption on cognitive function in women. N Engl J Med. 352(3):245-53

Stoclet JC, Chataigneau T, Ndiaye M, Oak MH, El Bedoui J, Chataigneau M, Schini-Kerth VB. (2004) Vascular protection by dietary polyphenols. Eur J Pharmacol. 500(1-3):299-313

Wessel, T (1984) The agricultural foundations of civilization, Agriculture and Human Values 1(2), 9:12.


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A grapefruit in the oven – does grapefruit juice negate the contraceptive pill?

The oral contraceptive pill consists of the synthetic hormones ethinyloestradiol (EE) and progestogen. It works by fooling a women’s body into thinking she’s pregnant – thus preventing further conception.

Grapefruit juice is one of the more commonly consumed fruit juices. For example 21% of US households purchase the juice regularly.

Grapefruit juice is broken down in the liver by one particular enzyme system (cytochrome P-450 3A4). This is the same enzyme system which breaks down estradiol (and other drugs). By utilising this system and “overloading” it, grapefruit juice can slow the breakdown of drugs such as estradiol. This could potentially elevate blood estradiol levels.

In a test-tube, reduced breakdown certainly occurs. Similarly in women lacking ovaries, grapefruit juice taken with oral hormones increased the level of estradiol in the blood.

So grapefruit juice interracts with oral hormones. But can this cause the failure of the contraceptive pill and unwanted pregnancies?

The jury is out on this. There appear to have been no known pregnancies as a result of grapefruit juice interraction with the pill. Furthermore, studies have used large quantities (several glasses worth) of grapefruit juice. Chances are then, that one or less glasses a day are probably fine.


Kane G.C., Lipsky J.J. (2000) Drug–Grapefruit Juice Interactions, Mayo Clin Proc. 75:933-942

Schubert W, Cullberg G, Edgar B, Hedner T (1994) Inhibition of 17 beta-estradiol metabolism by grapefruit juice in ovariectomized women. Maturitas, 155–63.

Schubert W, Eriksson U, Edgar B, Cullberg G, Hedner T, (1995) Flavonoids in grapefruit juice inhibit the in vitro hepatic metabolism of 17 beta-estradiol. Eur J Drug Metab Pharmacokinet 1995;3:219–24.

Weber A, Jager R, Borner A, Klinger G, Vollanth R, Matthey K, Balogh A (1996) Can grapefruit juice influence ethinylestradiol bioavailability? Contraception, 53:41–7.


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